1. Technical Field of the Invention
The present invention relates to transport network management system (TNMS) communication of operation and maintenance (O&M) information over an asynchronous transfer mode (ATM) network and, in particular, to the encapsulation of common management information protocol (CMIP) formatted operation and maintenance information for asynchronous transfer mode based transport.
2. Description of Related Art
Broadband transmission and switching have become important topics in the communications industry. A new system has been implemented for transmitting broadband and narrowband packet and circuit signals over a broadband network. This system is commonly referred to as asynchronous transfer mode (ATM). In ATM, data is packed into frames, with each frame segmented into a plurality of fixed length blocks called "cells." Each ATM cell is fifty-three bytes (or octets) long and consists of a five byte header indicating, as one of its functions, the destination of the cell, followed by a forty-eight byte payload containing the data to be transmitted to that destination.
The use of ATM cells permits the information transfer rate over the physical medium of the broadband network to adapt to actual service requirements. Depending on the capacity required, the number of cells per unit of time may be increased in a variable bit rate (VBR) ATM network up to the transmission bit rate limit of the physical medium. Alternatively, constant bit rates (CBR) are supported, with the transmission bit rate adjusted by the inclusion of idle or fill in cells when necessary. The cells are transported over the physical medium at a typical constant bit rate of, for example, 155.52 Mbits per second. Faster bit rates are supported for communications occurring solely within the ATM network.
One important characteristic of ATM technology relates to its protocol architecture and is built around the so-called "core-and-edge" principle. The protocol functions specific to the information type being transported, such as retransmissions, flow control, and delay equalization, are performed in user terminals at the "edges" of the ATM network. This leaves an efficient, service-independent "core" network, including only simple cell-transport and switching functions. A user-to-network interface (UNI) implementing an ATM adaptation layer (AAL) is provided at the "edge" of the network to connect the user terminals to the core network thereby allowing for service-independent ATM transport. The ATM adaptation layer performs a mapping operation between the bit stream data format of the user terminals external to the ATM network and the payload field of an ATM cell transmitted through the network.
In the field of transport network management (TNM) compliant network management systems, it is required that the interface with the network elements comprise a Q.sub.3 interface. The functionality to be provided under the Q.sub.3 interface is currently described in TMN Standard M.3010. The defined functionalities address the upper levels (4-7) of the International Standards Organization (ISO) Open Systems Interconnection (OSI) model. Some solutions have been proposed with respect to the transmission means (OSI levels 1-3) to be used for supporting the Q.sub.3 interface. This work has primarily focused on the use of the Transmission Control Protocol/Internet PROTOCOL (TCP/IP) for low speed communications, and the use of Fiber Distributed Data Interface (FDDI) for medium speed communications. What is needed in connection with high speed communications is a mechanism for utilizing an asynchronous transfer mode network as the transmission means for supporting the Q.sub.3 interface. Such a transmission means would accommodate real-time and low latency transport of operation and maintenance (O&M) data.
In previously filed, commonly assigned, co-pending application for patent Ser. No. 08/615,096, entitled "SYSTEM SUPPORTING VARIABLE BANDWIDTH ASYNCHRONOUS TRANSFER MODE NETWORK ACCESS FOR WIRELINE AND WIRELESS COMMUNICATIONS" filed Mar. 14, 1996, the disclosure of which is incorporated by reference, a system is disclosed which utilizes a multi-level data bit stream capable of supporting variable bandwidth ATM network access. The bit stream is dynamic in nature in that it is capable of supporting a number of different sub-rates with respect to its included channel bearers. To support repairability and configurability, the bit stream includes an embedded operation channel for transmitting operation and maintenance messages. Furthermore, to specify the use of the right amount of bandwidth at the proper location within the communications system, the bit stream includes delimiting data for performing add/drop multiplexing and/or digital cross-connection functions.
In particular, the disclosed multi-level data bit stream comprises a basic bit stream block including an appropriate repetition rate for the information being transmitted. The transmission bit rate of the basic bit stream block is a fraction of the transmission bit rate limit of the physical medium used in the ATM network. In instances where higher transmission bit rates are needed, for example in carrying video or data (file transfers), multiple basic bit stream blocks are used to carry the data during the same time period. The basic bit stream block further supports sub-rates useful in carrying voice and data communications in a plurality of channels. With respect to such sub-rate communications, delimiting data is added for performing add/drop multiplexing and/or digital cross-connection functions of the included channels. Furthermore, each basic bit stream block includes an embedded operation channel useful for connection maintenance, performance monitoring, path tracing, supervision and service management functions.
There would be an advantage if the disclosed multi-level data bit stream, and in particular its included embedded operation channel could be used as the mechanism for facilitating use of an asynchronous transfer mode network as the transmission means supporting the Q.sub.3 interface.